• Open Access

Phase II, Open-Label Trial of Single-Agent CCNU in Dogs with Previously Untreated Histiocytic Sarcoma


  • Dr Moore is presently affiliated with Veterinary Oncology Consultants, Wauchope, Australia. Dr Russell is presently affiliated with The Ohio State University, Columbus, OH. Dr Northrup is presently affiliated with College of Veterinary Medicine, University of Georgia, Athens, GA. Dr Kristal is presently affiliated with Chavat Daat Veterinary Specialty Center, Bet Berl, Kfar Saba, Israel. Dr Bailey is presently affiliated with Oradell Animal Hospital, Paramus, NJ. Dr Flory is presently affiliated with Veterinary Specialist Centre, North Ryde, Australia. Dr Kiselow is presently affiliated with Veterinary Medical Specialists, Campbell, CA. Dr Intile is presently affiliated with Veterinary Specialists of Rochester, Rochester, NY.

Corresponding author: Kenneth Rassnick, DVM, DACVIM, Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, P.O. Box 31, Ithaca, NY 14853; e-mail kmr32@cornell.edu.


Background: Histiocytic sarcoma (HS) is an aggressive neoplasm in dogs, and in most instances, the disease is localized, but not amenable to surgical removal, or is disseminated. Affected patients usually die within 6 months. There have been no prospective studies to determine efficacy of single-agent chemotherapy in dogs with HS.

Hypothesis: Single-agent CCNU [1-(2-chloroethyl)3-cyclohexyl-1-nitrosourea; lomustine] has antitumor activity against HS in dogs.

Animals: Twenty-one dogs with histologically confirmed, nonresectable localized or disseminated HS.

Methods: Prospective, open-label phase II clinical trial in which dogs with previously untreated HS were uniformly treated with CCNU as a single oral dosage of 90 mg/m2 every 4 weeks. The primary outcome measure was reduction in tumor size.

Results: Fourteen dogs with disseminated HS and 7 with localized HS were enrolled between 1999 and 2008. Overall response rate was 29% (95% confidence interval [CI], 14–50%) for a median of 96 days (95% CI, 55–137 days). Three dogs (1 disseminated, 2 localized) had complete responses lasting for 54–269 days and 3 dogs (2 disseminated, 1 localized) had partial responses lasting for 78–112 days.

Conclusions and Clinical Importance: CCNU, when used as a single agent, has activity against HS in dogs. Evaluation of CCNU postoperatively for dogs with resectable localized HS and as part of combination therapy for tumors that are nonresectable or disseminated should be considered.